Safety valve

Abstract

Safety valve, characterized in that it principally consists of a housing (1), provided with an inlet (2) and and outlet (3); a main cut off valve (4) installed in the housing (1); and means working together with the flow of liquid which with the removal of liquid and after a lapse of time shut the main cut off valve (4), which are reset in their starting position each time an equal or almost equal pressure in the liquid is created at the inlet (2) and outlet (3) of the safety valve and which when the main cut off valve (4) is shut, hold it shut as long as a well defined drop of pressure remains in existence over the main cut off valve (4), whereby these means are driven by means of a by-pass, such by means of a channel (6) that is situated apart from the main passage (5).

I claim: 
     
       1. A safety valve, comprising: a housing having an inlet, an outlet, a main passage, and a bypass channel;   a main cut-off valve installed in the housing;   means, actuated by the flow of liquid within the safety valve, for moving the main cut-off valve into a closed position after a predetermined period of time has lapsed and for holding the main cut-off valve in the closed position when a pressure drop exists across the main cut off valve, the moving and holding means being reset to a starting position each time a first pressure on liquid at the inlet and a second pressure on liquid at the outlet are approximately equal and including   a moving mechanism which after moving a specific stroke distance closes the main cut-off valve,   driving means, disposed in the bypass channel, for driving the moving mechanism   first resetting means for moving the moving mechanism into the starting position each time the main cut off valve is in an open position and liquid is not being removed from the safety valve;   second resetting means for moving the main cut-off valve from the closed position to the open position when the pressure drop across the main cut off valve is approximately zero;   a second cut-off valve disposed in the main passage which ensures that a substantially constant drop of pressure is created across the bypass channel;   a coupler having first and second coupling parts which can be engaged and disengaged with each other, the coupler being connected to the driving means and the moving mechanism; and   a servo device which engages with the coupler when a flow of liquid is created at the inlet such that when the first and second coupling parts are not engaged the first resetting means are set into operation.   
     
     
       2. A safety valve according to claim 1, further comprising means for allowing a new buildup of pressure behind the main cut-off valve after the main cut-off valve is in the closed position. 
     
     
       3. A safety valve according to claim 2, wherein the means for allowing the new buildup of pressure includes a connecting channel that connects a first space located before the main cut-off valve with a second space located after the main cut-off valve. 
     
     
       4. A safety valve according to claim 3, wherein the connecting channel includes means for regulating the flow of liquid therethrough. 
     
     
       5. A safety valve according to claim 4, wherein the means for regulating the flow includes an adjusting screw which can be screwed to regulate the flow of liquid through the connecting channel. 
     
     
       6. A safety valve according to claim 1, wherein the moving mechanism includes a rotatable element that engages with the coupler and is moved by the driving means, and a guiding mechanism cooperating with the main cut-off valve and the rotatable element such that when the guiding mechanism is moved over a defined angular distance, the main cut-off valve can move from the open position to the closed position. 
     
     
       7. A safety valve according to claim 6, wherein the rotatable element is connected to the main cut-off valve or is integrally produced with the main cut-off valve as a single piece. 
     
     
       8. A safety valve according to claim 6, wherein the guiding mechanism includes a lip which rotates with the rotatable element and a circular guide on which the lip rests and slides over, and wherein the circular guide has an axial notch such that when the lip enters the axial notch, the main cut-off valve is in the closed position. 
     
     
       9. A safety valve according to claim 6, further comprising a stop which determines the starting position of the rotatable element. 
     
     
       10. A safety valve according to claim 9, wherein the stop is movable, and further comprising means for adjusting a position of the stop. 
     
     
       11. A safety valve according to claim 10, further comprising a regulating element which is rotatable around the rotatable element, the regulating element including the stop. 
     
     
       12. A safety valve according to claim 11, wherein the regulating element further includes a rim gear and the adjusting means includes a rotatable shaft having teething thereon, the teething meshing with the rim gear. 
     
     
       13. A safety valve according to claim 6, wherein the first resetting means includes a torsion spring. 
     
     
       14. A safety valve according to claim 1, wherein the first and second coupling parts have first and second teething, respectively, the first and second teething meshing with each other. 
     
     
       15. A safety valve according to claim 6, wherein the first and second coupling parts have first and second teething, respectively, and the first and second teething can mesh with each other, and wherein the first coupling part is driven in a rotating manner by the driving means and the second coupling part is an integral part of or is connected to the rotatable element. 
     
     
       16. A safety valve according to claim 15, wherein the first and second coupling parts are rotatable along a common axis, and the first coupling part is movable along the common axis by the servo device, such that the first coupling part engages with the second coupling part. 
     
     
       17. A safety valve according to claim 15, wherein the driving means includes a turbine which is disposed in the bypass and which is coupled to the first coupling part. 
     
     
       18. A safety valve according to claim 17, wherein the first coupling part and the turbine are connected to each other via a plurality of worm and toothed wheel transmissions. 
     
     
       19. A safety valve according to claim 18, wherein the plurality of worm and toothed wheel transmissions create an overall transmission ratio of at least 1/3.000. 
     
     
       20. A safety valve according to claim 19, wherein the servo device includes an axially movable cut-off valve disposed in the inlet, and wherein the axially movable cut-off valve, when in an open position couples the first coupling part to the second coupling part, and the axially movable cut-off valve is forced into its closed position by means of a spring and is in its open position when a predetermined small pressure difference exists across the axially movable cut-off valve. 
     
     
       21. A safety valve according to claim 20, wherein the first coupling part and the axially movable cut off valve are axially disposed in relation to each other and are connected to each other by a telescopically collapsible connection, the collapsible connection having a stop and an elastic part which push apart the first coupling part and the axially movable cut-off valve into a maximum extended position such that in a position of rest the first coupling part is located in front of and does not engage with the second coupling part, and wherein when the first and second coupling parts engage each other, the axially movable cut off valve can still open against the force of the elastic part. 
     
     
       22. A safety valve according to claim 21, wherein the bypass channel has an inlet which faces toward the turbine and which is located downstream from a seat of the axially movable cut-off valve and upstream from a seat of the main cut-off valve. 
     
     
       23. A safety valve according to claim 20, wherein the second cut-off valve is disposed in the main passage downstream from the axially movable cut-off valve and is held in a closed position by a spring, and wherein when liquid is removed from the safety valve the second cut-off valve is opened by the pressure of liquid, and the inlet of the bypass channel begins in a space which is situated between the seat of the axially movable cut-off valve and the seat of the second cut-off valve. 
     
     
       24. A safety valve according to claim 23, wherein the spring keeps the second cut off valve in its closed position until a predetermined drop in pressure is created which causes the first and second coupling parts to engage and which delivers a first force that allows the main cut-off valve to move to its closed position against a second force of the second resetting means. 
     
     
       25. A safety valve according to claim 22, wherein the elastic part creates a first force which is greater than a second force created by the second resetting means. 
     
     
       26. A safety valve according to claim 23, wherein the axially movable and second cut-off valves are mounted concentrically, and further comprising a supple, pliable seal which is disposed between the axially movable cut-off valve and the second valve cut-off valve. 
     
     
       27. A safety valve according to claim 26, wherein the second resetting means includes a spring which exerts a comprehensive force on the main cut-off valve, in a direction opposite to a direction of the flow of liquid. 
     
     
       28. A safety valve according to claim 1, further comprising a flow rupture safety device disposed between the main cut-off valve and the guiding mechanism. 
     
     
       29. A safety valve according to claim 6, wherein the safety valve further comprise a flow rupture safety device including a coupling disposed between the main cut-off valve and the guiding mechansim, the coupling allowing a movement of the main cut-off valve up to its seat, and a flow rupture spring mounted in the coupling which only allows the movement of the main cut-off valve with respect to the guiding mechanism when a predetermined high difference in pressure over the main cut-off valve exists.